This Guide can be used to flash both models as they are very similar but all you have to do is use special firmware files for each one.
Run NSpro software program.
From model list Select C260 and click on Next button.
Click on Flash button.
From Baudrate drop down menu select 921600 for faster process.
You need to use C260 NSpro cable and the phone battery must be out.
Click on Browse button beside Write File field and select: C260xxxxx.s3.
Click on Write button and connect Cable to phone to start the process.
Do not touch or remove cable from phone till all is done.
Notice: In case your phone has some software problems you can flash it with Repair Mode option Checked but you will lost the IMEI number of this phone so after flashing process finished you need to rewrite your phone IMEI again.